Abstract
This study investigated the tribological behaviour of Pongamia oil (PO) and 15W–40 mineral engine oil (MO) with and without the addition of graphene nanoplatelets (GNPs). The friction and wear characteristics were evaluated in four-ball anti-wear tests according to the ASTM D4172 standard. The morphology of worn surfaces and the lubrication mechanism of GNPs were investigated via SEM and EDS. This study also focuses on the tribological effect of GNP concentration at various concentrations. The addition of 0.05 wt % GNPs in PO and MO exhibits the lowest friction and wear with 17.5% and 12.24% friction reduction, respectively, and 11.96% and 5.14% wear reduction, respectively. Through SEM and EDS surface analysis, the surface enhancement on the worn surface by the polishing effect of GNPs was confirmed. The deposition of GNPs on the friction surface and the formation of a protective film prevent the interacting surfaces from rubbing, resulting in friction and wear reduction.
Highlights
Energy demand has been precipitously increasing due to the increase in population and rapid modernization and industrialization globally
Carbon was detected on mineral engine oil (MO) worn surfaces; this can be attributed to the base oil containing the undefined carbonbased additive, and because carbon is the sub-element of steel balls
The tribological effects of graphene nanoplatelets (GNPs) on mineral oil and Pongamia oil were investigated by a four-ball test in accordance with ASTM D4172
Summary
Energy demand has been precipitously increasing due to the increase in population and rapid modernization and industrialization globally. A good combination of base oils and additives to formulate the lubricants will play a critical role in this improvement. Many studies have recently been carried out on nanoparticles’ application as lubricant additives in the tribology field. Most of these studies reported that the addition of nanoparticles to base oils enhanced the tribological performance [10,11,12,13]. Jason et al [26] mentioned four main parameters of nanoparticles that affect the tribological properties: (1) concentration, (2) size, (3) morphology, and (4) dispersion stability. After a series of tribo-testing, worn surfaces were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS)
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